1. Field of the Invention
The subject invention is directed to cardiac leads, and more particularly, to a low profile active fixation cardiac pacing lead having a torque transmitting mechanism for activating the fixation helix at the distal end of the lead.
2. Description of Related Art
Current active fixation leads are designed with an extendable and retractable fixation helix or screw, that can be retracted for transvenous insertion of the lead into the right atrium and ventricle and then extended so that the lead can be actively screwed into the endocardial wall.
Direct drive leads in which the fixation screw can be extended/retracted by a stylet shaped with a screwdriver tip are known. It is also known to connect the connector pin of the lead connector (e.g., IS-1 connector) to the fixation screw by way of the inner conductor coil. The direct drive mechanism has some advantages in that a straight or preformed J-shaped stylet can be introduced at the same time the helix is extended or retracted. The conductor coil drive mechanism is disadvantageous in that there is a delay in the transmission of torque from the connector pin to the helix.
In addition, the coil driven type requires a coaxial lead body design as compared to an inline lead body, since the inner conductor coil has to be turned relative to the outer connector coil. Such a design tends to increase the overall cross-sectional profile of the lead body. The subject invention overcomes the disadvantages associated with the drive mechanism in prior art active fixation leads.